Necrotizing fasciitis (NF) is a rare, rapidly progressive bacterial infection. Periorbital NF may spread from the eyelid into the posterior orbit. Extent of the infection is critical in planning surgical debridement. A diabetic 70-year-old man presented with a black wound and severe pain in the left periorbital area following a mild trauma. Clinical findings were consistent with NF involving the eyelids, temporal and malar regions. In addition, he had proptosis, diffuse ophthalmoplegia, and central retinal artery occlusion, suggesting deep orbital involvement. Computed tomography showed soft tissue abnormalities in the anterior orbit. The patient was successfully treated with subcutaneous debridement, antibiotherapy, and metabolic support. Periorbital NF may be complicated with posterior orbital cellulitislike symptoms and retinal vascular occlusions, possibly because of remote vascular thrombi induced by bacterial toxins. This clinical manifestation should be distinguished from true bacterial invasion of the posterior orbit, which may require more aggressive surgical treatments such as exenteration.